1. Field of the Invention
The presently disclosed and claimed inventive concept(s) relates generally to substrates useful for performing biological, chemical and diagnostic assays as well as methods of producing and using same.
2. Description of the Background Art
Microarray technology has emerged as a powerful tool in life science and biomedical research. Microarrays are excellent tools for testing a large number of known different molecules against unknown substances. A microarray usually consists of a solid support (such as a glass slide, silicon wafer, and nylon- or polymer-based substrate) that contains numerous different reagents immobilized on its surface in a pre-arranged manner. These reagents (known as probes, capture phases or capture agents) are usually selected for their high specialty and reactivity, such as binding, affinity, toward their counterparts (known as targets) found in biological samples. After applying a biological sample onto a microarray under an experimentally-controlled condition, the interactions between each probe on a microarray and its corresponding target in the biological sample can be observed through various target labeling techniques and appropriate detection instrumentation, thereby providing the microarray use with qualitative and quantitative information about the target in the tested biological sample.
Microarrays can be synthesized on a substrate according to an assortment of methods. For example, to produce a microarray directly on a substrate, one may employ methods of solid-phase chemical synthesis in combination with site-directing mass as disclosed in U.S. Pat. No. 5,510,270. Alternatively, one may use photolithographic techniques involving precise drop deposition via piezoelectric pumps, as disclosed in U.S. Pat. No. 5,474,796, incorporated herein by reference. Or, one may contact a substrate with typographic pins holding droplets and using ink jet printing mechanisms to lay down a microarray matrix as disclosed in U.S. Pat. No. 5,807,522, incorporated herein by reference.
Background binding of proteins, carbohydrates, cell lysates and the like to the surface of glass or other substrates employed in a microarray which include microspots containing protein capture agents or the like has posed a problem for a number of years. Non-specific binding of proteins to a microarray substrate increases the background noise when the microarray is imaged or the signals generated on the microspots are otherwise read; this makes it difficult to detect and distinguish signals being obtained from labels which should be specifically bound to particular spots, particularly in instances where the signal is relatively weak, because such background noise interferes and prevents obtaining precise readings.
A common method being used to lower non-specific binding involve manners of blocking the regions of the surface of the substrate surrounding each of the plurality of microspots after capture phase binding. The blocking method comprises contacting the surface with a charged polymer or a compound that has good non-specific binding itself after attachment of a capture phase but before a detection step, such as, contacting the microarray with a target moiety. The charged compound negates a substrate surface of an opposite charge. It cancels and masks the influence of the substrate. However, this process can reduce affinity reactions between affinity phase and sample. The problem with the current state of the art is that typically higher binding of the capture phase leads to greater non-specific binding.
Adhesion of a capture phase to a surface is related to the surface energies and the electrostatic charges of the surface and the capture phase. Surface energies depend on hydrophilic and hydrophobic nature of the materials. Electrostatic charges depend on the charge densities and counter charges between the capture phase and the surface. Unfortunately, the factors affecting binding of a capture phase to a surface are the same ones affecting non-specific binding of a protein to the surface.
Thus, it is an object of the presently disclosed and claimed inventive concept(s) to provide a substrate having a high binding of a capture phase and low non-specific binding, and a microarray using such a substrate, that overcomes the defects and disadvantages of the prior art.